This project investigates the expression of proto-oncogenes during the differentiation of embryonic lens epithelial cells to form lens fiber cells and seeks to determine the specific function of the corresponding gene products in the developing lens. The normal developmental profile of each of three nuclear proto-oncogenes, c-myc, c-fos, and c-jun, has been investigated in order to correlate expression of these genes with cell growth, differentiation, and expression of lens-specific genes. Information concerning proto-oncogene action in the lens is provided by studies of the exact timing of proto-oncogene expression in relation to cell division, cell differentiation, and expression of specific genes. In particular, we have attempted to correlate expression of specific proto-oncogene mRNAs with expression of mRNAs for proteins such as heat-shock protein (HSP70) and calpactin, whose expression and/or activity has been shown to be regulated by specific proto-oncogenes in other cell types. Finally, the effects of growth factors on protooncogene expression are being studied to provide a basis for organ culture of lenses.